When I first saw a Northern Harrier, the etymology traced back, made sense. The bird splashed from the prairie—like a reverse dive—and dropped a vole just a few feet in front of me. The harrier swung low over the grass: flapping its wings, teetering, and soaring, as it looked back towards me and I noticed its owl-like face. I knew the word, harrier. It’s a military jet that can take off and land vertically, that strafes low over battlefields. In that instant of flight, the word’s meanings changed for me. The bird’s flight looks like the jet’s flight. Or rather, the jet moves like the bird. The meaning of a raptor changed for me too that day. I knew of peregrine falcons, eagles, osprey, and vultures. This harrier was different.
Northern Harrier acrobatics (photo by Andy Reago & Chrissy McClarren).
In the harrier is a splendid symmetry with its environment. Its adaptations are remarkable, a physiology and suite of traits harnessed for the grassland and marshland habitat. The Harrier slides, like a chess piece across the board. The Harrier dips and banks with its long and narrow tail, its movements as natural as a feather floating to the earth. The Harrier listens, hearing with its facial disk that directs sound to its ears. The Harrier hunts, taking the best traits from many other raptors: mid-flight, hovering, on-foot, vulturing. The Harrier dances, males in spring, spiraling through the air like a giddy pilot. The Harrier, hawk of marshes.
There was a time when harriers didn’t dance. The DDT years. Fran Hamerstrom, who found time to produce a 25-year study on Northern Harriers during her landmark research on the Prairie Chickens of central Wisconsin’s Buena Vista Grasslands, noted the decline. She linked DDT to a crashing number of breeding harriers in the years 1965-1970.
Harriers are endangered in Iowa. They are uncommon in southern Wisconsin, where they enjoy grasslands of 250 acres or more. They like to nest in wet areas in wet prairies, among cattails, bluejoint, or prairie cord grass. Heavily modified agricultural landscapes do not support many Northern Harriers, but the birds frequent Faville Grove, where the grassland habitat is rapidly expanding. In the past few weeks we’ve seen fleeting glances of a Harrier pair. We’ve looked for a nest, for evidence of fledgling young, or for the adults carrying doomed voles. These birds haunt the lowland prairies near the Crawfish River, which must contain abundant voles. I have been lucky enough to observe harriers haunting these prairies for years, the gray ghost male and the larger, brown and reigning female.
The silvery male Northern Harrier in flight (photo by Mick Thompson).
Fran Hamerstrom was a singular character, full of personality and ingenuity. She worked on the harrier project on the side, unpaid but persistent. She once perceived criticism from the Conservation Department, and quipped “You don’t mind if I play bridge in my spare time do you? . . . Well I’d rather trap hawks than play bridge.”
She collected dozens of harrier biopsies and stored them in her freezer. Unable to pay the expensive lab fee for each sample, Fran waited. One day, a man showed up at her house. She told him to go look at the eagles by the shed, but the man stayed and talked about raptors and DDT. He was invited to stay for lunch. Then dinner. Fran made one of her famous pies and they soon had a deal: the man—who worked in California analyzing biopsy samples—would analyze the samples for Fran. In exchange, Fran sent pies.
In exchange for sitting on the nest, the female harrier is rewarded with an easy meal from the male. He will cruise along, meadow vole in talons, and drop the vole into the air, where the female catches it on the wing. Often, the female will land two or three times before she returns to the nest, in order to confuse any watchful predators.
Fran Hamerstrom teaches students at her home in Plainfield, WI c. 1950s (UW Digital Archives).
Fran’s work began with a simple question: Do harriers mate for life? Her scientific inquiry led to a quarter century of research and the mentoring of hundreds of “gaboons,” her faithful field workers who helped trap, band, and track the breeding harriers for the season. She was the cook for her crew of gaboons and made pies and cakes but hid them in the house from the gaboon’s ravenous appetites. Fran lamented that she couldn’t hide the ice cream anywhere but the freezer.
A small mouse, the meadow vole, rules over the harrier’s diet. The vole population cycles every four years, crashing and rising. The number of harrier nests and fledglings corresponds directly with the number of voles in an area. The number of polygynous harriers increases during high vole years. In high vole years, conditions are good, and the “wealthy” male breeders can afford more than one mate.
A debutante, Fran shunned a wealthy inheritance on the east coast for the marshes of central Wisconsin. She recognized the necessity of banding individual birds to realize individual case histories—to learn about migration routes, breeding pairs, and lifespan. Of course, she used rings accumulated from childhood and attached them to the birds. She eventually ran out of rings and had to modify the bands for the Harrier project. She used plastic strips designed for outdoor furniture on the harriers for identification. The company who made these strips discontinued them, and Fran hoarded her meager supply.
Northern Harrier female foraging in a prairie at Goose Pond Sanctuary (photo by Arlene Koziol).
The Northern Harrier seems a truly American bird. A fierce hunter, a bit paranoid around the nest, a graceful soarer, and a reveler in the wealth of abundant voles, the bird fits into the American conscience as it fits onto the grasslands of the continent. In her book on harriers, Fran says “modern man prefers to ignore the value of fire, prevent floods, and get rid of beaver.” In essence, society loathes the disturbance associated with early successional habitat of the harrier and so the harrier is loathed. But I wonder if the harrier is even noticed; prairie is more often encountered as a new subdivision name than a real living prairie.
L to R: Rugh Durgan, Aldo Leopold, Frederick and Frances Hamerstrom in 1934 (photo via WCHoF, courtesy of Elva Hamerstrom Paulson).
Fran Hamerstrom finished her harrier study at age 75, and died 15 years later in 1998. In the Buena Vista Marsh, Fran found a wealth of questions that sustained her, from Prairie Chickens to harriers and kestrels. She developed ingenious methods for catching and marking these animals for further study. Despite her limited supplies and budget, Fran was a scientist in the truest sense, and she made lasting relationships, first with her husband Frederick, and also with thousands of gaboons, students, and colleagues. Her obituary in the New York Times stated: “She only occasionally swept around the piles of turtle shells, snowshoes, wildlife gear, books and files, all of which served as evidence of what it was that pleased her.”
In the harrier, we see a bird tied to what it must love: meadow voles, fires, floods, and sweeping grasslands. A simple mantra structures the bird’s life: live free.
Written by Drew Harry, Faville Grove Sanctuary land steward
Cover photo via Pixabay. A brown female Northern Harrier, with an owl-like face, is mid-flight.
